title: GLUT-1 mediation of rapid glucose transport in dolphin (Tursiops truncatus) red blood cells.
abstract: D-Glucose entry into erythrocytes from adult dolphins (Tursiops truncatus) was rapid, showed saturation at high substrate concentrations, and demonstrated a marked stimulation by intracellular D-glucose. Kinetic parameters were estimated from the concentration dependence of initial rates of tracer entry at 6 degrees C: for zero-trans entry, Michaelis constant (K(m)) was 0.78 +/- 0.10 mM and maximal velocity (Vmax) was 300 +/- 9 mumol.l cell water-1.min-1; for equilibrium exchange entry, K(m) was 17.5 +/- 0.6 mM and Vmax was 8,675 +/- 96 mumol.l cell water-1.min-1. Glucose entry was inhibited by cytochalasin B, and mass law analysis of reversible, D-glucose-displaceable, cytochalasin B binding gave values of 0.37 +/- 0.03 nmol/mg membrane protein for maximal binding and 0.48 +/- 0.10 microM for the dissociation constant. Dolphin glucose transporter polypeptides were identified on sodium-dodecyl sulfate-polyacrylamide gel electrophoresis immunoblots [using antibodies that recognized human glucose transporter isoform (GLUT-1)] as two molecular species, apparent relative molecular weights of 53,000 and 47,000. Identity of these polypeptides was confirmed by D-glucose-sensitive photolabeling of membranes with [3H]cytochalasin B. Digestion of both dolphin and human red blood cell membranes with glycopeptidase F led to the generation of a sharp band of relative molecular weight 46,000 derived from GLUT-1. Trypsin treatment of human and dolphin erythrocyte membranes generated fragmentation patterns consistent with similar polypeptide structures for GLUT-1 in human and dolphin red blood cells.
authors.affiliation: Chemistry Department, Bishop's University, Lennoxville, Quebec, Canada.
authors.forename: J D
authors.initials: JD
authors.lastname: Craik
authors.forename: J D
authors.initials: JD
authors.lastname: Young
authors.forename: C I
authors.initials: CI
authors.lastname: Cheeseman
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism*; D015153:Blotting, Western; D003571:Cytochalasin B / Q000097:blood / Q000494:pharmacology; D004289:Dolphins / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D051272:Glucose Transporter Type 1; D006801:Humans; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000097:blood* / Q000302:isolation & purification; D014316:Tritium
chemical_list: D001786:Blood Glucose; D051272:Glucose Transporter Type 1; D009004:Monosaccharide Transport Proteins; C495677:SLC2A1 protein, human; D014316:Tritium; D003571:Cytochalasin B